1. Field of the Invention
The present invention relates to a substrate processing method and a substrate processing system.
2. Description of the Related Art
In a photolithography process in a fabrication process of, for example, a semiconductor wafer (hereinafter referred to as a “wafer”), a resist solution is coated onto a surface of the wafer, and the wafer undergoes a resist coating treatment for forming a resist film, an exposure processing for exposing a pattern to the wafer, a developing treatment for developing the wafer after the exposure and the like, so that a predetermined circuit pattern is formed on the wafer.
As the resist coating treatment, a dominant method today is a spin-coating method which discharges the resist solution to the center of the rotated wafer to diffuse the resist solution over the surface of the wafer.
However, since the wafer is rotated a high speed according to the spin-coating method, high volume of the resist solution scatters from the peripheral edge part of the wafer, and therefore a lot of the resist solution is wasted. Additionally, since the unit is contaminated by the scatter of the resist solution, there are disadvantages that the unit needs to be cleaned frequently and so on.
Hence, instead of the spin-coating method which rotates the wafer, a method of discharging the resist solution onto the wafer while relatively moving the wafer and a resist solution discharge nozzle so that a path of a resist solution discharge part becomes a rectangular wave shape with large amplitude, which results in that the wafer is coated evenly with the resist solution in a plurality of parallel lines, that is, a method of coating of the so-called one continuous writing stroke is conceivable. In this coating method of one continuous writing stroke, there is a possibility that the surface of the resist film after the coating swells along the coating path of the resist solution, and hence it is preferable to use the resist solution having low viscosity which spreads easily over the wafer after the coating, and to flatten the coating film after completion of the coating.
By the way, it is recently demanded to further narrow the so-called “edge cutting width”, which is at the peripheral edge part of the substrate and is not commercialized, and hence a technology for narrowing the edge cutting width needs to be developed in the above-described coating method of the so-called one continuous writing stroke as well. In order to narrow the edge cutting width, it is necessary to increase the viscosity of the resist solution so that the resist solution in the periphery of the wafer does not swell.
However, when the viscosity of the resist solution is increased in the coating method of one continuous writing stroke, the resist solution discharged onto the wafer becomes hard to be spread and to be smoothed in flattening processing after that, and hence film thickness is thickened along the coating path of the resist solution, and an in-plane uniformity of the resist film is decreased. Namely, in the coating method of the so-called one continuous writing stroke, lowering the viscosity of the resist solution in order to narrow the edge-cutting width and maintaining the in-plane uniformity of the resist solution are inconsistent to each other.